Ok. I was hoping that you had the later style system that you can input in the phone and then the passkey was what you inputed.
Unfortunately there is no override. The first thing would be to call you dealership that you have your vehicle serviced at and maybe they will have it in the vehicles service history so they can check and tell you the code.
If not, you will need to set up an appointment. It will only take about a half hour. They will need to read out the vehicle with their tester and then manually retrieve the code from the TCU(telephone control unit). That is the only way to obtain the bluetooth passkey if lost. I hope this information is helpful. Thank you.
BMW Mechanic
Level 1 BMW Master Certification, 9 Years Dealer experience, Team Leader, Shop Foreman